Macromonomers

Macromonomers are macromolecules that contain a polymerizable functional group at one or more chain ends, enabling them to act as monomeric units in polymerization reactions. This allows polymer chains to grow by incorporating pre-formed polymer segments, which can lead to materials with architectures not readily accessible from small-molecule monomers alone. Common outcomes include graft copolymers, block copolymers with bulky side chains, and star- or bottlebrush-shaped polymers.

Types and preparation methods vary, but macromonomers are typically polymers bearing a reactive end group such as a vinyl, norbornene, acrylate, or epoxide. They are usually prepared by attaching a polymerizable group to a polymer via living or controlled polymerization techniques or by post-polymerization modification. The resulting end functionality must remain reactive under the intended polymerization conditions.

Applications of macromonomers include the synthesis of complex architectures through methods such as living polymerization, ROMP, ATRP, or RAFT. For example, macromonomers with norbornene end groups can be polymerized by ring-opening metathesis polymerization to form bottlebrush polymers with predefined side chains. They are also used to create block copolymers where a bulky pre-formed segment is incorporated as a repeating unit, as well as to generate graft and star polymers with controlled topology.

Considerations in their use include keeping the end-group reactivity intact during handling, managing steric hindrance from bulky macromonomers, and ensuring compatibility of the macromonomer with the chosen polymerization mechanism.